Lifting Apparatus for Subsea Equipment

ABSTRACT

A lifting apparatus for subsea equipment and a method of installing subsea equipment for a subsea well. A lower marine riser package (LMRP) including elevator links that pivot on a load bearing structure located on the LMRP. An elevator link can include a stem coupled between a pivot loop and a crane loop releasably attachable to a crane block on a hoisting mechanism, such as a gantry crane. The elevator link can be configured to support at least some of the weight of the LMRP. The elevator links can be adjusted to a predetermined spacing between crane blocks by pivoting the elevator links on pivot points located on the load bearing structure.

BACKGROUND

This section is intended to provide background information to facilitate a better understanding of the various aspects of the described embodiments. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art.

In most offshore drilling operations, a wellhead at the sea floor is positioned at the upper end of the subterranean wellbore lined with casing, a blowout preventer (BOP) stack is mounted to the wellhead, and a lower marine riser package (LMRP) is mounted to the BOP stack. The upper end of the LMRP typically includes a flex joint coupled to the lower end of a drilling riser that extends upward to a drilling vessel at the sea surface. A drill string is hung from the drilling vessel through the drilling riser, the LMRP, the BOP stack, and the wellhead into the wellbore.

During drilling operations, drilling fluid, or mud, is pumped from the sea surface down the drill string, and returns up the annulus around the drill string. In the event of a rapid invasion of formation fluid into the annulus, commonly known as a “kick”, the BOP stack and/or LMRP may actuate to help seal the annulus and control the fluid pressure in the wellbore. In particular, the BOP stack and LMRP include closure members, or cavities, designed to help seal the wellbore and prevent the release of high-pressure formation fluids from the wellbore. Thus, the BOP stack and LMRP function as pressure control devices.

The LMRP and BOP stack are large, heavy pieces of subsea equipment that often require the use of a gantry crane to be moved or lifted into position. For example, to move the LMRP or the LMRP coupled to the BOP stack within an offshore oil rig, the LMRP can be hoisted using the gantry crane on the rig. In some situations, the LMRP attaches to the gantry crane using a lift ring coupled to a load shoulder of the LMRP. The LMRP lift ring can have as few as two lift points coupled to the load shoulder of the LMRP. Typically, the lift ring is securely fastened to the load shoulder. Each lift point on the lift ring is equally spaced from the center of the LMRP to match a crane block spacing on the offshore vessel (e.g., an offshore oil rig). Thus, the lift points can have a fixed center-to-center spacing (e.g., 2500 mm, 2750 mm, 2800 mm, etc.). The crane block spacing can vary from offshore vessel to offshore vessel. This requires the lift rings to be specifically fabricated according to the crane block spacing available on the offshore vessel. It requires a long lead time and a generous amount of welding and machining to ensure the lift ring matches the crane block spacing, resulting in a costly design.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the embodiments of the invention, reference will now be made to the accompanying drawings in which:

FIGS. 1a and 1b depict a schematic view of an offshore system for drilling and/or producing a wellbore, according to one or more embodiments; and

FIG. 2 depicts a schematic view of a crane block assembly and a subsea BOP stack assembly, according to one or more embodiments.

DETAILED DESCRIPTION

This disclosure provides lifting points for subsea equipment. Specifically, the disclosure provides lifting points on a lower marine riser package (LMRP) including elevator links that pivot within the LMRP to adjust to multiple crane block spacings.

An LMRP can include a riser flex joint, a riser adapter, a BOP (such as an annular BOP), and control units. The LMRP can serve as an additional pressure control system in conjunction with the BOP stack. The LMRP can be a large, heavy piece of subsea equipment that often requires the use of a gantry crane to be moved or lifted on an offshore vessel and, in the rare emergency situation, from the seabed using a heavy lift vessel. The LMRP can include elevator links that mount to a load bearing structure of the LMRP via a pinned connection. The elevator links can be designed to pivot and be adjusted to fit a variety of crane block spacings available on offshore vessels. The elevator links can be constrained to provide a stable lifting mechanism. Further, the elevator links can be used to lift the LMRP or the LMRP with a subsea BOP stack attached.

FIGS. 1a and b show an offshore drilling system 3 including an offshore vessel 5, a subsea BOP stack assembly 10, and a wellhead assembly 11. The offshore vessel 5 includes a crane 7 (such as a gantry crane) that can be used to move or hoist the BOP stack assembly 10 while it is onboard the offshore vessel 5. For example, the crane 7 may be used to move the BOP stack assembly over the moon pool of the offshore vessel 5. The wellhead assembly 11 is formed at the upper end of a bore into the seabed 12. The BOP stack assembly 10, in this example, includes a lower marine riser package 15 (LMRP) and a BOP stack 16. The LMRP 15 and the BOP stack 16 are connected in such a way that there is a continuous bore 20 from the lower end of the BOP stack 16 through to the upper end of the LMRP 15. The lower end of the BOP stack 16 is connected to the upper end of the wellhead 11 and is sealed in place. The upper part of the LMRP 15 can connect to the end of a riser pipe 22, which connects the BOP assembly 10 to the offshore vessel 5 shown in FIG. 1 a.

Within the bore 20, a tubular string 23 is provided. Such a string may incorporate a number of different types of components, including simple piping, joint members, bore guidance equipment and may have attached at its lower end, a test tool, a drill bit or a simple device which allows the circulation or the flow of desired fluids through the well. Alternatively, the string 23 may take the form of casing, tubing, coiled tubing, wire line or cables, or other components which is necessary to pass through the BOP stack assembly 10 into the wellhead 11.

FIG. 2 shows the crane 7 and the BOP stack assembly 10, in accordance with one or more embodiments. The LMRP 15 can include a lifting assembly 200 to attach the LMRP 15 to the crane 7 or any other suitable hoisting mechanism. The lifting assembly 200 includes elevator links 210 that adjustably attach to the crane 7. As an example, the elevator link 210 can include a stem 211 coupled between a pivot loop 212 and a crane loop 213 releasably attachable to the crane 7. Each elevator link 210 may be made of any material suitable for supporting weight, for example, each elevator link 210 can include a unitary forged body comprising a steel alloy.

Referring to FIGS. 1a and 2, an offshore lifting system 30 can include the crane 7 and the BOP stack assembly 10 with the lifting assembly 200. The crane 7 can include two or more crane blocks 31. The crane 7 can attach to the LMRP 15 using the crane blocks 31 and move the LMRP 15 within the offshore vessel 5. In particular, the crane blocks 31 can be axially spaced from each other based on a predetermined, fixed spacing 33 (e.g., 2500 mm, 2750 mm, or 2800 mm, etc.). In one or more embodiments, the crane blocks 31 can include extension devices 35 that are configured to mate with the crane loops 213 of the lifting assembly 200 and support the weight of the BOP stack assembly 10 as it is hoisted and moved by the crane 7.

The spacing between the crane loops 213 can be adjusted by pivoting the elevator links 210 on pins 214 to fit within the predetermined spacing 33 to allow the crane loops 213 to releasably couple to the crane blocks 31. To do so, each elevator link 210 is adjustably coupled to a load bearing structure 215 at the pivot loop 212 using the pin 214 and a locking plate (not shown) received in the pin 214 to secure the pin 214 and the elevator link 210 to the load bearing structure 215. The load bearing structure 215 can include a stab plate on the LMRP 15. The pins 214 can include a pin, peg, bolt, or other protrusion located on the load bearing structure 215. The pins 214 can include any suitable device configured to receive the pivot loop 212 and support at least some of the weight of the LMRP 15 on the load bearing structure 215. Optionally, the pins 214 pass through the pivot loops 212 and into ports 216 located on the load bearing structure 215. In one or more embodiments, the pins 214 may be integral with the load bearing structure 215. The pins 214 allow the elevator links 210 to pivot on the pivot loops 214 in the directions indicated by the arrows 220 to match the predetermined spacing 33 of the crane blocks 31.

The lifting assembly 200 can include one or more constraining devices(s) 217 to releasably couple the elevator links 210 to each other and/or to the LMRP structure. In one or more embodiments, the constraining device 217 may include one or more clamps, fasteners, or any suitable fastening device. The constraining 217 can stabilize the connection between the crane blocks 31 and the lifting assembly 200. In one or more embodiments, the constraining device 217 can create a fixed connection between the crane 7 and the lifting assembly 200 by preventing the elevator links 210 from pivoting on the pins 214. The elevator links 210 can be positioned to have a spacing from the crane loops 213 within the predetermined spacing 33 of the crane blocks 31.

With the elevator links 210 properly adjusted and secured, the crane blocks 31 can be releasably coupled to the elevator links 210. Once attached to the crane blocks 31, the LMRP 15 can be moved, raised, lowered, or positioned within the offshore vessel 5 using the crane 7.

The lifting assembly 200 can have a load capacity sufficient to lift the load of the LMRP 15, the load of the BOP stack assembly 10, or the load of the LMRP 15 mounted to one or more devices. In one or more embodiments, the lifting assembly 200 can have a load capacity of up to about 500 metric tons or more. The load bearing structure 215 can support this load at the pins 214. The lifting assembly 200 can be used to hoist the LMRP 15, the BOP stack assembly 10, or any suitable arrangement of the LMRP 15 mounted to one or more devices. A subsea BOP stack such as the BOP stack 16 can be engageable with the load bearing structure 215 such that the LMRP 15 supports the BOP stack 16 while the LMRP is hoisted by the crane 7 of FIG. 1

This discussion is directed to various embodiments of the invention. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function, unless specifically stated. In the discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. In addition, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. The use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components.

Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims. 

What is claimed is:
 1. A lower marine riser package (LMRP), comprising: a load bearing structure comprising a pin; and an elevator link coupled to the load bearing structure and pivotable on the pin, the elevator link configured to support at least some of the weight of the LMRP.
 2. The LMRP of claim 1, further comprising a subsea blowout preventer (BOP) stack engageable with the load bearing structure such that the subsea BOP stack is supportable by the LMRP.
 3. The LMRP of claim 1, wherein the load bearing structure comprises a stab plate.
 4. The LMRP of claim 1, wherein the elevator link comprises a loop releasably attachable to a crane block.
 5. The LMRP of claim 1, wherein the elevator link comprises a loop and an additional loop axially spaced from the loop, wherein the loop is coupled to the additional loop via a stem.
 6. The LMRP of claim 5, wherein the elevator link is coupled to the load bearing structure through the pivot loop.
 7. The LMRP of claim 1, further comprising: an additional pin located on the load bearing structure; and an additional elevator link coupled to the load bearing structure and pivotable on the additional pin.
 8. The LMRP of claim 7, further comprising a constraining device coupled to the elevator link and the additional elevator link, wherein the constraining device is configured to prevent the elevator links from pivoting on the pins.
 9. The LMRP of claim 7, wherein the elevator links are configured to support at least one of (a) up to about 500 metric tons and (b) more than 500 metric tons.
 10. A method of positioning a lower marine riser package (LMRP), comprising: adjusting elevator links to a predetermined spacing by pivoting the elevator links on pins located on a load bearing structure located on the LMRP; releasably coupling the elevator links to crane blocks axially spaced by the predetermined spacing; and positioning the LMRP by moving the crane blocks.
 11. The method of claim 10, further comprising: releasably coupling a subsea blowout preventer (BOP) stack to the LMRP; and positioning the LMRP and the BOP stack.
 12. The method of claim 10, further comprising coupling a constraining device to the elevator links so that the elevator links are positioned at the predetermined spacing and prevented from pivoting on the pins.
 13. The method of claim 10, wherein at least one elevator link of the elevator links comprises a loop and an additional loop axially spaced from the loop, wherein the loop is coupled to the additional loop via a stem.
 14. The method of claim 10, wherein at least one elevator link of the elevator links comprises a loop removeably attachable to at least one crane block of the crane blocks.
 15. The method of claim 10, further comprising coupling the elevator links to the load bearing structure at the pins.
 16. The method of claim 10, wherein positioning comprises moving the LMRP using a crane with the crane blocks.
 17. The method of claim 10, further comprising supporting at least one of (a) up to about 500 metric tons and (b) more than 500 metric tons using the elevator links.
 18. An offshore lifting system, comprising: a crane comprising crane blocks axially spaced by a predetermined spacing; a lower marine riser package (LMRP) comprising: a load bearing structure comprising a pin; and an elevator link coupled to the load bearing structure and pivotable on the pin, the elevator link configured to support at least some of the weight of the LMRP; and a subsea blowout preventer (BOP) stack releasably coupled to the load bearing structure such that the subsea BOP stack is supportable by the LMRP.
 19. The offshore lifting system of claim 18, wherein the LMRP further comprises: an additional pin located on the load bearing structure; an additional elevator link coupled to the load bearing structure and pivotable on the additional pin; and a constraining device coupled to the elevator link and the additional elevator link, wherein the constraining device is configured to prevent the elevator links from pivoting on the pins.
 20. The offshore lifting system of claim 19, wherein the elevator links are configured to support at least one of (a) up to about 500 metric tons and (b) more than 500 metric tons, and wherein an additional constraining device is coupled to the LMRP and the elevator link. 